Problem: 8 binders cost $15.76. Which equation would help determine the cost of 2 binders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 8 binders. We want to know the cost of 2 binders. We can write the numbers of binders as a proportion: $\dfrac{8}{2}$ We know 8 binders costs $15.76. We can let $x$ represent the unknown cost of 2 binders. The proportion of these costs can be expressed as: $\dfrac{\$15.76}{x}$ The cost changes along with the number of binders purchased, and so the two proportions are equivalent. $\dfrac{8}{2} = \dfrac{\$15.76}{x}$